Page 201 - Pressure Swing Adsorption

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178 PRESSURE SWING ADSORPTION DYNAMIC MODELING OF A PSA SYSTEM 179

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Figure 5.1 (Continued).

TIME, S Extended Langmuir Model
(al
Figure 5.1 (a) Pressure profile m a small PSA column seoaratmg air on 5A zeolite (5.13)
for oxygen production. The steps in sequence are depressunzaoon (30 s), purge_ (30 s),
pressunzat1on (30 s), and production (90 s). The pressure drop during the production !=I
step 1s due to additional product withdrawal for purging the other bed. Column size:
90 cm Oength)XlO cm ·(i.d.), bed voidage=0.35. (From Ref. 31; reprmted with
permission.) (b) A representative pressure-tune history m a small PSA column
separntmg air on molecular sieve RS-10 for mtrogen production. The steps m LRC Model
seQuencc arc oressurizalion (15 s), high-pressure feed (35 s), blowdown (6 s), and
purge (3 s). Column size: 101.6 cm (length) X 2.08 cm (i.d.), bed voidage = 0.6. (From qf b;cf;
Ref. 32; reprmted with permission.) _.c,_ = ---n,,.c.-- (5.14)
qis "'"'
1 + L, b,.cf;
,- !
accurate representation of the Henry·s Law region 1s obviously essential; so The LRC model 1s essentially the mult1comoonent extension of the hybrid
from this perspective the Langmutr equation 1s preferable. Langmuir-Freundlich eouatmn. In the Langmmr-Freundlich eouat10n the
The bulk PSA separation processes that have so far been modeled are for concentration terms are raised to arbitrary exponents to provide an improved
tile most part bin·~~1es. together with a few ternary systems. To predict the empincal fit of the smgle-component data. Both extended Langinmr and
~uxture isotherms the extended Langmuir modei, the loading ratio correla- LRC mocteis orovide explicit expressions for the adsorbed phase concentra•
tion (LRC) and ideal adsorbed solution theory OAS) have been applied. tions. so no iteration 1s needed during the simulation. By contrast. the IAS